The invention generally concerns a seat and more particularly a sprung vehicle seat.
Various kinds of sprung vehicle seat are already in use in different types of vehicles. One form of such a seat comprises a base surface member for mounting to the vehicle structure and a top surface member intended for example to carry a seat squab. The seat includes a spring member for providing the springing effect, while operatively disposed between the base member and the top member is a scissor support assembly comprising first and second lateral scissor levers or arms. The scissor levers are each fixed by one end thereof while their second end remote therefrom is movable to permit a scissor action on the part of the scissor support assembly. The scissor levers are pivotably connected together by means of a suitable spindle or shaft. Mounted to the first scissor levers is a sliding guide which is oriented in the longitudinal direction of the seat and against which bears the spring member which is adjustable for weight adjustment of the seat, in the longitudinal direction of the seat. Reference may be made to DE 30 42 604 C2 to find a seat design of that nature.
Due to the actual structure involved however that known vehicle seat cannot be less than a given minimum heightwise dimension, that is to say, in regard to the heightwise setting of the top member in relation to the base member.
Reference may also be made to U.S. Pat. No. 5,871,198 for a vehicle seat of similar sprung nature. That vehicle seat however involves a multiplicity of individual components, and the assembly thereof represents a not inconsiderable expenditure in terms of time and labor.
An object of the present invention is to provide a sprung vehicle seat which is of a simple design configuration and simple to manufacture and which is such that the spacing between the base and top members in the condition of maximum loading on the seat can be extremely small.
A further object of the present invention is to provide a sprung vehicle seat which is of a rational structure with a small number of components with little susceptibility to wear and which can also be of a very compact structure in the heightwise direction thereof.
Still another object of the present invention is to provide a sprung vehicle seat which affords easy weight adjustment for the seat occupant.
In accordance with the principles of the present invention the foregoing and other objects are attained by a sprung vehicle seat comprising a base surface member, a top surface member, and a scissor support assembly operatively disposed between the base member and the top member and having first and second lateral scissor levers each having a first end which is fixed and a second end which is remote from the first end and which is movable. The scissor levers are pivotably connected together by means of a pivot spindle or shaft. Fixed to the first scissor levers and oriented in the longitudinal direction of the seat is a sliding guide against which a spring member bears. The spring member is adjustable for weight adjustment of the vehicle seat, in the longitudinal direction of the seat. The sliding guide is in the form of a plate member which in the non-loaded condition of the vehicle seat is oriented at least approximately parallel to the top member. Arranged on the plate member slidably in the longitudinal direction of the seat is a first slide member for fixing the first end portion of the spring member, being the lower end thereof. Arranged at the underside of the top member slidably in the longitudinal direction of the seat is a second slide member for fixing the second end portion of the spring member, being the upper end thereof. The first slide member and the second slide member are connected together by means of the spring member and are thus displaceable simultaneously in the longitudinal direction of the seat for weight adjustment of the vehicle seat.
As will be apparent from the description hereinafter of a preferred embodiment of the invention, the fact that the sliding guide is in the form of a plate member which for example may involve a sheet metal member which is connected by welding to the two lateral first scissor levers means that it is possible for the vehicle seat overall to be of a small structural height, in comparison with a seat having a sliding guide which is oriented perpendicularly as is used in above-mentioned DE 30 42 604 C2 or in comparison with wedge surfaces which are also oriented perpendicularly or inclinedly upwardly and downwardly as are used in above-mentioned U.S. Pat. No. 5,871,198. In addition, the plate member which constitutes the sliding guide is comparatively easy and thus inexpensive to produce. The same applies in regard to the first and second slide members between which the spring member is disposed. The spring member can be arranged loosely between the two slide members. Simultaneous displacement of the first and second slide members with the spring member arranged therebetween, for weight adjustment of the vehicle seat, can be effected for example by means of a spindle drive or by means of a displacement arrangement as is described in German patent application No 100 39 501.5.
In a preferred feature of the vehicle seat according to the invention the spring means can be formed by a conical spiral spring which increases in width from the first end portion which is at the lower end to the second end portion which is at the upper end, wherein the first slide member has a holding projection adapted to the first end portion of the spiral spring and the second slide member has a collar adapted to the second end portion of the spiral spring. Such a design configuration affords the advantage that it ensures a reliable operative connection between the first and second slide members by means of the spiral spring, in spite of being loosely combined with the two slide members, while in addition ensuring optimum displaceability of the spring between the plate member forming the sliding guide and the top member of the vehicle seat. A further advantage of such a vehicle seat design configuration is that the structural height thereof, that is to say the spacing between the base member and the top member of the vehicle seat, can be very small when the spiral spring is in the xe2x80x98coil-boundxe2x80x99 condition, that is to say when the coils of the spiral spring are in a condition of bearing against each other and the spring is thus solid.
In a further preferred feature of the invention the spring means of the vehicle seat can for example also comprise a block of a suitable plastic material, which enjoys suitable spring properties.
In a further preferred feature of the vehicle seat according to the invention the plate member forming the sliding guide has a main portion extending forwardly in the longitudinal direction of the seat from the scissor support assembly pivot in a direction towards the fixed end of the two lateral first scissor levers, and a secondary portion extending rearwardly in the opposite direction to the first-mentioned direction. The scissor support assembly pivot is at a central region of the vehicle seat, that is to say, of the seat cushion or squab which is disposed on the top member of the vehicle seat. That central region is also correspondingly loaded by the respective occupant of the seat. If the spring means is displaced in the longitudinal direction of the seat into the proximity of the scissor support assembly pivot, that denotes a weight setting of the seat for a seat occupant of heavier weight. If on the other hand the spring means is displaced forwardly away from the scissor support assembly pivot, that denotes a weight setting for an occupant of lighter weight. That can be explained by virtue of the turning moment of the spring force of the spring means and the associated lever arm between the spring means and the fixed ends of the two lateral first scissor levers, which compensates for the turning moment which is determined by the weight of the user and the lever arm of that weight in relation to the fixed end of the first scissor levers.
In another preferred feature of the invention the main portion and/or the secondary portion of the plate member forming the sliding guide has an abutment which, when the vehicle seat is in the lowest condition thereof in which the spring is compressed, bears against the base member of the vehicle seat. That provides for precisely and definedly establishing the lowermost position of the vehicle seat in which the spring is fully compressed, when the seat therefore involves the minimum structural height thereof.
As the spring means is provided between the first and second slide members of the vehicle seat, in such a way that the spring means presses with a given, low level of mechanical bias against the plate member forming the sliding guide and the top member of the vehicle seat, a certain amount of friction which is proportional to that biasing force is inevitable upon longitudinal displacement of the spring means for weight adjustment of the seat. In order to remove that frictional effect, a preferred feature of the invention can provide that a flexible non-stretchable member is tensioned between the lower and upper end portions of the spring member, with a pre-loading spring member operatively disposed between the base member and the top member of the seat. The flexible non-stretchable member between the lower and upper end portions of the spring means or between the two slide members may be a non-stretchable band or cable which is disposed between the end portions of the spring means or between the slide members in such a way that the spring means bears precisely between the plate member and the top member of the vehicle seat without however pressing against the plate member and the top member. That eliminates friction upon longitudinal displacement of the spring means between the plate member and the top member of the seat. A further advantage of such a design configuration is that it makes it easier to assemble the spring means in the seat. The pre-loading spring member of the seat affords in that respect the advantage that it is capable of compensating at least for the weight of the vehicle seat, that is to say, all the seat components above the base member of the seat. Preferably however the seat uses a pre-loading spring member which is also suitable for compensating for the weight of a light seat occupant. Then the spring member which is operatively disposed between the plate member and the top member of the vehicle seat and which is displaceable in the longitudinal direction of the seat for weight adjustment thereof can advantageously be so dimensioned that it only has to be capable of compensating for or setting the weight difference between a light occupant and a heavy occupant.
Further objects, features and advantages of the invention will be apparent from the description hereinafter of two embodiments of a vehicle seat according to the invention.